Influence of strain estimation methods on life predictions using the local strain approach

The influence of strain estimating techniques on life predictions using the local strain approach has been studied. Strain prediction methods included Neuberʹs rule in its original form and a generalized form, the equivalent strain energy density method, and the finite element analysis using ABAQUS code. Life predictions were made using the local strain method for two aluminium coupons (7050-T7451), one with a Low Kt of 1.4 and the other with a High Kt of 3.25, under two different load spectra. The predictions were compared to the results of five fatigue tests per coupon type and spectrum. The comparisons showed that the strain estimation technique has little influence on the prediction accuracy compared to the experimental data scatter. Also, a significant difference in relative prediction accuracy between the High and Low Kt coupons was found. It was attributed to different proportions of time spent in fatigue initiation and propagation for the two coupons.